This is Steven Salzberg's blog on genomics, pseudoscience, medical breakthroughs, higher education, and other topics, including skepticism about unscientific medical practices. Here's where I can say what I really think about abuses and distortions of science, wherever I see them.

Eating fish is good for you, especially fish that contain omega-3 fatty acids. So I was surprised last week to read a new study in the Journal of the National Cancer Institute that found that omega-3 fatty acids increase the risk of prostate cancer. The risk for both high-grade and low-grade cancer was increased with higher levels of omega-3 fatty acids. This is a carefully done study, and the results should make anyone who is taking fish oil pills reconsider.

One reason this study caught many people off guard is that there has been much evidence showing that a diet rich in fish that contain omega-3 oils is good for you. The Mayo Clinic says that "eating fish helps your heart", especially fish like salmon that contain omega-3 fatty acids. The American Heart Association (AHA) elaborates:

"Omega-3 fatty acids benefit the heart of healthy people, and those at high risk of — or who have — cardiovascular disease. Research has shown that omega-3 fatty acids decrease risk of arrhythmias (abnormal heartbeats), which can lead to sudden death. Omega-3 fatty acids also decrease triglyceride levels, slow growth rate of atherosclerotic plaque, and lower blood pressure (slightly)."

This all sounds great. Because of the evidence about the benefits of fatty fish, supplement manufacturers have been marketing and selling fish oil pills for years, with great success. As I described back in 2010, GlaxoSmithKline even created a high-dose omega-3 fatty acid pill called Lovaza that has FDA approval.

But the evidence for that you can get the same benefit from supplemental omega-3 fatty acids — taking a pill, that is — is much weaker. In fact, a large review published last year in the Journal of the American Medical Association found no connection at all between supplemental omega-3 and a lower risk of heart attacks, strokes, or death in general. Other studies have reported similarly negative results. So it appears that fish oil pills may not have any heart benefits.

And now, with this new study, we learn that supplemental fish oil might increase the risk of prostate cancer.

The bottom line: the AHA recommendations about eating fish are probably still good ones. The AHA website says:

"We recommend eating fish (particularly fatty fish) at least two times (two servings) a week. Each serving is 3.5 oz. cooked, or about ¾ cup of flaked fish. Enjoy fish baked or grilled, not fried."

But popping a fish oil pill is not going to cut it. As we've seen before, supplements often fail to show the benefits that a healthy diet offers. So save your money and stop buying those fish oil pills — and fire up the grill and throw on a few salmon fillets for this weekend's barbecue.

My institution had a bit of good news this week. The latest U.S. News rankings of the nation's top hospitals just appeared, and Hopkins has regained the number 1 spot, which it temporarily lost last year. We've been number 1 for 22 of the past 23 years. See the story here.

I'd like to think this is, in part, because Hopkins Medicine has been one of the foremost institutions in the world at pursuing science-based and evidence-based medicine.

One of the coolest scientific discoveries of the past few years was a small bone found in a remote region of Siberia. The scientists who found it initially thought it was just an early human fossil, or else a Neanderthal fossil, but something about it looked a bit off. It was just one small finger bone, not much to go on.

But DNA sequencing told a different tale. The bone belonged to a female who was neither human nor Neanderthal, but something in between. She and her kind appear to be closer to Neanderthals than to modern humans, but there is no doubt that she represents a new hominid species, one that died out only recently in evolutionary terms. The evidence indicates that this previously unknown group, called the Denisovans after the cave in which the bone was found, actually interbred with humans.

The latest findings were published last fall in the journal Science, by a team led by Matthias Meyer and Svante Paabo. With just one small, 75,000-year-old finger bone, they knew that extracting DNA would be a challenge. Most of the DNA from ancient samples comes from bacteria and other creatures that have infiltrated the bone over the millenia. But they were lucky in one respect: Siberia is cold, and has been for a very long time, which helps to preserve DNA. Still they had to develop an entirely new method of extracting ancient DNA for this bone.

Meyer and colleagues extracted enough DNA to cover the entire genome of this ancient female. They estimated that Denisovans and human diverged over 175,000 years ago. They also discovered that modern Papuans contain vestiges of Denisovan DNA in their genomes, about 6%, suggesting that interbreeding occurred when humans were spreading across Asia.

Just this month, National Geographic's Jamie Shreeve published a feature article on the discovery, providing a fascinating look at how a single finger bone revealed a previously lost sister species. (I highly recommend it, even for those who read the original Science article.) Now that we know what to look for, we might find more, and learn more, about these almost-humans from ancient Siberia. And maybe we'll eventually figure out why they disappeared.

A final note: this discovery is yet another example of how evolution has shaped the history of life on this planet, but somehow I suspect the anti-evolution forces in the U.S. will find a way to deny it.